Conventionally, electrical fuse devices (electrical fuse circuits) are configured using electrical fuse elements made of polysilicon or the like and are widely used for semiconductor integrated circuits (LSI) of trimming program devices of high-frequency semiconductor devices. In semiconductor integrated circuits including such electrical fuse devices, electrical fuse elements are blown by applying a large current of about 1 A with bipolar transistors, so that programming is performed.
In recent years, for semiconductor integrated circuits, a process has been developed in which a metallic material is formed as a gate material on polysilicon by silicification and the resistance of the gate material is reduced. Accordingly, a technique for electrical fuse elements has become available. The technique uses a mechanism for cutting a silicide layer on a top surface and increasing a resistance by passing current through a gate material. In the case of 130-nm and 90-nm process generations, when electrical fuse elements are fed with current and blown, blowing requires an instantaneous carrying current of 10 to 30 mA for each electrical fuse element.
When such an electrical fuse device is used for a trimming device or the like of a high-frequency device, the number of mounted electrical fuse elements is not more than four to eight for one chip of a system LSI. Thus, the electrical fuse elements can be blown at a time using a tester.
The following will describe such a conventional electrical fuse device (for example, National Publication of International Patent Application No. 11-512879, page 31, FIG. 3) used for a semiconductor integrated circuit.
FIG. 9 is a circuit diagram showing a structural example of an electrical fuse device conventionally used for a semiconductor integrated circuit. In FIG. 9, reference numeral 31 denotes an electrical fuse element, reference numeral 32 denotes a PMOS transistor connected in series with the electrical fuse element 31, and reference numeral 33 denotes an NAND circuit having its output connected to the gate of the PMOS transistor.
The blowing operation of the electrical fuse device will be discussed below.
A program signal is inputted to the NAND circuit 33. When the PMOS 32 is turned on by the program signal, current is passed through the electrical fuse element 31 which has been program selected. The electrical fuse element 31 is formed of a fine pattern of silicide, polysilicon, or metal. The electrical fuse element 31 is heated and blown by a predetermined current and thus has a break and a higher resistance. The initial resistance of the electrical fuse element having not been programmed is read and a resistance of the electrical fuse element having been programmed with a high resistance is read, so that a signal state 0/1 can be recognized. The electrical fuse device can be obtained thus.
In recent years, as system LSIs have become larger in size, the number of installed memories increases. The more memories are installed, the number of defective memory cells increases. Further, the number of defective memory cells has been further increased by finer design rules. In order to repair defective memories, metal fuses are conventionally used for redundancy repair of RAM such as DRAM and SRAM.
However, electrical fuse elements for cutting silicide on poly have recently become available. Since such electrical fuse elements can be blown with a small current, elements surrounding the fuse elements are less affected and damaged and the circuit configuration of an electrical fuse device can be equal to or smaller than that of a metal fuse. Thus, such an electrical fuse device can be used for RAM redundancy as well as a trimming device of a high-frequency device and are growing in demand.
The number of electrical fuse elements mounted for RAM redundancy repair in a system LSI is 500 to 1000 for one chip. In the case of 130 nm and 90 nm process generations, when electrical fuse elements are brought into conduction and blown, blowing requires an instantaneous carrying current of 10 to 30 mA for each electrical fuse element. Hence, when such an electrical fuse device is used for RAM redundancy repair, programming for 1000 electrical fuse elements at a time requires an instantaneous carrying current of about 10 A.
However, it is difficult for an existing general-purpose tester to supply a current of 10 A according to the program and supply a current of 10 A concentratedly to an electrical fuse device in an LSI chip, so that a special tester is necessary.
Even in the case where 1000 electrical fuse circuit blocks are separately provided as an electrical fuse device and electrical fuse elements are blown one by one, a number of control terminals are necessary (one electrical fuse circuit block with four control terminals requires 4000 control terminals). Thus, such an electrical fuse device cannot be mounted in a system LSI. For this reason, such an electrical fuse device cannot be mounted for RAM redundancy repair in a system LSI.